/**
 * Insert a custom theme to project style file. If no valid style file could be found, a new
 * Scss file for the custom theme will be created.
 */
function insertCustomTheme(project: WorkspaceProject, projectName: string, host: Tree,
                           workspace: WorkspaceSchema) {

  const stylesPath = getProjectStyleFile(project, 'scss');
  const themeContent = createCustomTheme(projectName);

  if (!stylesPath) {
    if (!project.sourceRoot) {
      throw new SchematicsException(`Could not find source root for project: "${projectName}". ` +
        `Please make sure that the "sourceRoot" property is set in the workspace config.`);
    }

    // Normalize the path through the devkit utilities because we want to avoid having
    // unnecessary path segments and windows backslash delimiters.
    const customThemePath = normalize(join(project.sourceRoot, defaultCustomThemeFilename));

    if (host.exists(customThemePath)) {
      console.warn(yellow(`Cannot create a custom Angular Material theme because
          ${bold(customThemePath)} already exists. Skipping custom theme generation.`));
      return;
    }

    host.create(customThemePath, themeContent);
    addThemeStyleToTarget(project, 'build', host, customThemePath, workspace);
    return;
  }

  const insertion = new InsertChange(stylesPath, 0, themeContent);
  const recorder = host.beginUpdate(stylesPath);

  recorder.insertLeft(insertion.pos, insertion.toAdd);
  host.commitUpdate(recorder);
}

  return (host: Tree) => {
    const workspace = getWorkspace(host);
    const project = getProjectFromWorkspace(workspace, options.project);
    const styleFilePath = getProjectStyleFile(project);

    if (!styleFilePath) {
      console.warn(red(`Could not find the default style file for this project.`));
      console.warn(red(`Please consider manually setting up the Roboto font in your CSS.`));
      return;
    }

    const buffer = host.read(styleFilePath);

    if (!buffer) {
      console.warn(red(`Could not read the default style file within the project ` +
        `(${italic(styleFilePath)})`));
      console.warn(red(`Please consider manually setting up the Robot font.`));
      return;
    }

    const htmlContent = buffer.toString();
    const insertion = '\n' +
      `html, body { height: 100%; }\n` +
      `body { margin: 0; font-family: Roboto, "Helvetica Neue", sans-serif; }\n`;

    if (htmlContent.includes(insertion)) {
      return;
    }

    const recorder = host.beginUpdate(styleFilePath);

    recorder.insertLeft(htmlContent.length, insertion);
    host.commitUpdate(recorder);
  };

  it('should add material app styles', async () => {
    const tree = await runner.runSchematicAsync('ng-add-setup-project', {}, appTree).toPromise();
    const workspace = getWorkspace(tree);
    const project = getProjectFromWorkspace(workspace);

    const defaultStylesPath = getProjectStyleFile(project)!;
    const htmlContent = tree.read(defaultStylesPath)!.toString();

    expect(htmlContent).toContain('html, body { height: 100%; }');
    expect(htmlContent).toContain(
        'body { margin: 0; font-family: Roboto, "Helvetica Neue", sans-serif; }');
  });

  return (tree: Tree) => {
    const project = getProject(tree, options.project);
    const stylesPath: string = getProjectStyleFile(project, 'scss') as string;

    if (!tree.exists(stylesPath)) {
      throwSCSSRequiredForCustomizableThemes();
    }

    createThemeSCSS(tree, options.theme, project.sourceRoot as string);
    insertThemeImportInStyles(tree, stylesPath);


    return tree;
  }